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FreeBSD-SA-05:11.gzip                                       Security Advisory
                                                          The FreeBSD Project

Topic:          gzip directory traversal and permission race vulnerabilities

Category:       contrib
Module:         gzip
Announced:      2005-06-09
Credits:        Ulf Harnhammar, Imran Ghory
Affects:        All FreeBSD releases
Corrected:      2005-06-08 21:26:27 UTC (RELENG_5, 5.4-STABLE)
                2005-06-08 21:27:44 UTC (RELENG_5_4, 5.4-RELEASE-p2)
                2005-06-08 21:29:15 UTC (RELENG_5_3, 5.3-RELEASE-p16)
                2005-06-08 21:29:53 UTC (RELENG_4, 4.11-STABLE)
                2005-06-08 21:30:43 UTC (RELENG_4_11, 4.11-RELEASE-p10)
                2005-06-08 21:31:16 UTC (RELENG_4_10, 4.10-RELEASE-p15)
CVE Name:       CAN-2005-0988, CAN-2005-1228

For general information regarding FreeBSD Security Advisories,
including descriptions of the fields above, security branches, and the
following sections, please visit
<URL:http://www.freebsd.org/security/>.

I.   Background

gzip is a file compression utility.

II.  Problem Description

Two problems related to extraction of files exist in gzip:

The first problem is that gzip does not properly sanitize filenames
containing "/" when uncompressing files using the -N command line
option.

The second problem is that gzip does not set permissions on newly
extracted files until after the file has been created and the file
descriptor has been closed.

III. Impact

The first problem can allow an attacker to overwrite arbitrary local
files when uncompressing a file using the -N command line option.

The second problem can allow a local attacker to change the
permissions of arbitrary local files, on the same partition as the one
the user is uncompressing a file on, by removing the file the user is
uncompressing and replacing it with a hardlink before the uncompress
operation is finished.

IV.  Workaround

Do not use the -N command line option on untrusted files and do not
uncompress files in directories where untrusted users have write
access.

V.   Solution

Perform one of the following:

1) Upgrade your vulnerable system to 4-STABLE or 5-STABLE, or to the
RELENG_5_4, RELENG_5_3, RELENG_4_11, or RELENG_4_10 security branch
dated after the correction date.

2) To patch your present system:

The following patches have been verified to apply to FreeBSD 4.10,
4.11, 5.3, and 5.4 systems.

a) Download the relevant patch from the location below, and verify the
detached PGP signature using your PGP utility.

# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:11/gzip.patch
# fetch ftp://ftp.FreeBSD.org/pub/FreeBSD/CERT/patches/SA-05:11/gzip.patch.asc

b) Execute the following commands as root:

# cd /usr/src
# patch < /path/to/patch
# cd /usr/src/gnu/usr.bin/gzip
# make obj && make depend && make && make install

VI.  Correction details

The following list contains the revision numbers of each file that was
corrected in FreeBSD.

Branch                                                           Revision
  Path
- -------------------------------------------------------------------------
RELENG_4
  src/gnu/usr.bin/gzip/gzip.c                                    1.10.2.1
RELENG_4_11
  src/UPDATING                                             1.73.2.91.2.11
  src/sys/conf/newvers.sh                                  1.44.2.39.2.14
  src/gnu/usr.bin/gzip/gzip.c                                   1.10.26.1
RELENG_4_10
  src/UPDATING                                             1.73.2.90.2.16
  src/sys/conf/newvers.sh                                  1.44.2.34.2.17
  src/gnu/usr.bin/gzip/gzip.c                                   1.10.24.1
RELENG_5
  src/gnu/usr.bin/gzip/gzip.c                                    1.11.2.1
RELENG_5_4
  src/UPDATING                                            1.342.2.24.2.11
  src/sys/conf/newvers.sh                                   1.62.2.18.2.7
  src/gnu/usr.bin/gzip/gzip.c                                    1.11.6.1
RELENG_5_3
  src/UPDATING                                            1.342.2.13.2.19
  src/sys/conf/newvers.sh                                  1.62.2.15.2.21
  src/gnu/usr.bin/gzip/gzip.c                                    1.11.4.1
- -------------------------------------------------------------------------

VII. References

http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-0988
http://cve.mitre.org/cgi-bin/cvename.cgi?name=CAN-2005-1228
http://marc.theaimsgroup.com/?l=bugtraq&m=111271860708210
http://marc.theaimsgroup.com/?l=bugtraq&m=111402732406477

The latest revision of this advisory is available at
ftp://ftp.freebsd.org/pub/FreeBSD/CERT/advisories/FreeBSD-SA-05:11.gzip.asc
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